Acoustic touch apparatus

ABSTRACT

An improved acoustic touch apparatus that has a logo or application icon applied on the back surface of a propagating substrate which can be viewed through the substrate and an acoustic element situated adjacent the logo or application icon that can compensate for phase velocity shifts of surface acoustic waves in propagating over the logo or application icon.

FIELD OF THE INVENTION

This invention generally relates to acoustic touch sensors and, moreparticularly, to surface acoustic wave (SAW) touch screens.

BACKGROUND OF THE INVENTION

Touch sensor systems, such as touch screens or touch monitors, can actas input devices for interactive computer systems used for variousapplications, for example, information kiosks, order entry systems,video displays, mobile communications, etc. Such systems may beintegrated into a computing device, thus providing interactive touchcapable computing devices, including computers, electronic book readers,or mobile communications devices.

Generally, touch sensor systems enable the determination of a positionon the surface of a substrate via a user's touch of the surface. Thetouch substrate is typically made of some form of glass which overlies acomputer or computing device display, like a liquid crystal display(LCD), a cathode ray tube (CRT), plasma, etc. The touch sensor system isoperatively connected to the device display so that it also enables thedetermination of a position on the device display and, moreover, of theappropriate control action of a user interface shown on the display.

Touch sensor systems may be implemented using different technologies.Acoustic touch sensors, such as ultrasonic touch sensors using surfaceacoustic waves, are currently one of the available touch sensortechnologies and many types of acoustic touch sensors now exist. Forexample, an “Adler-type” acoustic touch sensor uses only two transducersper coordinate axis to spatially spread a transmitted surface acousticwave signal and determines the touch surface coordinates by analyzingtemporal aspects of a wave perturbation from a touch. For each axis, onetransducer at a respective peripheral surface generates surface acousticwave pulses that propagate through the substrate along a perpendicularperipheral surface along which a first reflective grating or array isdisposed. The first reflective array is adapted to reflect portions of asurface acoustic wave perpendicularly across the substrate along pluralparallel paths to a second reflective array disposed on the oppositeperipheral surface. The second reflective array reflects the surfaceacoustic wave along the peripheral surface to a second transducer wherethe wave is received for processing. The reflective arrays associatedwith the X axis are perpendicular to the reflective arrays associatedwith the Y axis so as to provide a grid pattern to enabletwo-dimensional coordinates of a touch on the substrate to bedetermined. Touching the substrate surface at a point causes a loss ofenergy by the surface acoustic waves passing through the point of touch.This is manifested as an attenuation of the surface acoustic waves andis detected by the receiving transducers as a perturbation in thesurface acoustic wave signal. A time delay analysis of the data is usedto determine the surface coordinates of a touch on the substrate.

An acoustic touch sensor may have a large number of operative elements(either multiple transducers, or transducer and reflective arraycombinations) disposed on, and along, the front peripheral surfaces ofthe substrate. In order to prevent damage due to exposure from theenvironment or external objects, the housing for these sensors or forthe devices integrating a sensor may include a bezel for the frontperipheral surfaces of the touch substrate that hides and protects theseperipheral operative elements, so that only an active touch region onthe front surface of the substrate is exposed for possible touch input.For bezel-less acoustic touch sensors, the peripheral operative elementsmay be located on the back peripheral surfaces of the substrate (in thiscase, a surface acoustic wave propagates around a substrate roundededge, across the front surface, and around the opposite substraterounded edge to reach the receiving elements). Thin-width bezel andbezel-less acoustic touch sensors each enlarge the active touch regionto essentially the whole front surface of the substrate, which may bebeneficial for small-sized integrated devices, like a smartphone, atablet computer, an electronic book reader, or other mobile computingdevice.

As the active touch region enlarges, more device features and touchfunctions may be provided in the active touch region. In some cases,however, these additional features and functions may interfere with thepropagation of surface acoustic waves on the touch substrate. Forexample, in many bezel-less systems that have certain aestheticconsiderations, the periphery of the back surface of the substrate mayhave an opaque ink or paint applied thereon with the peripheraloperative elements, such as the reflective arrays and transducers, beingprinted on top of the “border paint” so that these elements are hiddenfrom view through the typically transparent substrate. Further, a logoor application icon may be printed directly on the periphery of the backsurface of the substrate underneath the border paint. This permits theprinted logo or application icon to be seen through the substrate.Alternatively, the paint may be applied over (as described below) a cutout in the border paint having the shape of the logo or icon. However, adip in the received signals at the receiving transducers as well as asharp phase difference of the received surface acoustic waves may beobserved at the location of the printed logo or application icon. Inparticular, observations show that there is a definite dip in thereceived signal and sharp phase differences in the received surfaceacoustic waves that correspond to the start of the printed material ofthe icon or application icon and again at the end of the printedmaterial. Generally, it is believed that a surface acoustic waveexperiences changes in velocity in passing over the printed material(and thus loses phase coherence) resulting in the observed effects. Thepaint layering and the likely, slower velocity of propagation of theprinted material suggest reasons for the observed effects.

More specifically, it is believed that several types of reduced signalmay result because of the printed material. In a first case that theprinted material partially overlaps the reflective arrays, the signaldownstream of the printed material slopes downward. This can beattributed to the printed material slightly redirecting the surfaceacoustic waves. In the second case that the printed material completelyor mainly overlaps the reflective arrays, the signal downstream of theprinted material is depressed. This can be attributed to the attenuationof horizontal surface acoustic waves going through the printed materialpaint. If the printed material extends below the reflective arrays, adip in the received signal at the start of the printed material, becauseof the phase difference, is regularly observed. There should be anotherdip in the received signal at the end of the printed material, again dueto the phase difference; however, this is not usually observed, possiblybecause it is masked. Also, if the printed material extends below thereflective arrays, the dip in the received signal will have the width ofthe printed material. This is due to the attenuation of the surfaceacoustic waves traveling in the vertical direction away from thereflective array.

It would be advantageous to have an improved acoustic touch apparatusthat compensates for certain of the effects of surface acoustic wavevelocity changes in passing over the printed material and averts reducedreceived signals that may result.

SUMMARY OF THE INVENTION

The above problems are obviated by the present invention which providesan acoustic touch apparatus, comprising a substrate having surfacescapable of propagating surface acoustic waves; at least one acousticwave transducer on a first surface; and at least one reflective array onthe first surface, said transducer capable of transmitting or receivingsurface acoustic waves to or from the reflective array and saidreflective array capable of acoustically coupling surface acoustic wavesto propagate between surfaces of the substrate, and said substratehaving a first acoustic element disposed on the first surface thatintercepts propagating surface acoustic waves on the first surface andcauses variations in the phase velocity of the propagating surfaceacoustic waves and a second acoustic element disposed on the firstsurface that equalizes the variations. The second acoustic element maycancel out the phase advance or delay of any portion of the propagatingsurface acoustic waves intercepted by the first acoustic element. Thesecond acoustic element may be disposed on the first surface inproximity to the first acoustic element or as physically close aspossible to the first acoustic element.

Also, the second acoustic element may be adapted to interceptpropagating surface acoustic waves intercepted by the first acousticelement. In such case, the second acoustic element may counteract thephase advance of any portion of the propagating surface acoustic wavesintercepted by the first acoustic element. Also, the second acousticelement may be adapted to intercept propagating surface acoustic wavesparallel to the propagating surface acoustic waves intercepted by thefirst acoustic element. In such case, the second acoustic element maycounteract the phase advance of a portion of the propagating surfaceacoustic waves parallel to the propagating surface acoustic wavesintercepted by the first acoustic element.

The first acoustic element may comprise a cut-out of a layer ofacoustically benign material applied along the border of the firstsurface and a patch of acoustic material applied over the cut-out. Thelayer of acoustically benign material may comprise a first opaque inkand the patch comprises a second opaque ink having different visualproperties than the first opaque ink. Alternatively, the first acousticelement may comprise a cut-out of a layer of acoustically benignmaterial applied along the border of the first surface and an acousticmaterial filling in the cut-out, said first and second materials beingvisually distinguished from one another.

Alternatively, the first acoustic element may comprise acoustic materialapplied on the first surface and disposed under a layer of acousticallybenign material applied along the border of the first surface. In suchcase, the layer of acoustically benign material may comprise a firstopaque ink and the acoustic material of the first acoustic elementcomprises a second opaque ink having different visual properties thanthe first opaque ink. Also, the second acoustic element may compriseacoustic material disposed adjacent the first acoustic element andeither over or under the layer of acoustically benign material appliedalong the border of the first surface. In such case, the first acousticelement may comprise a plurality of shapes and the second acousticelement is formed with a shape that is a composite of the plurality ofthe shapes of the first acoustic element, or the first acoustic elementmay comprise a plurality of separated shapes and the second acousticelement comprises a plurality of separated segments that areinterspersed with the shapes, each segment disposed adjacent arespective shape and at least partially intercepting a portion of thepropagating surface acoustic waves that are parallel to the propagatingsurface acoustic waves intercepted by the respective shape.

Alternatively, the second acoustic element may comprise acousticmaterial disposed adjacent the cut-out over the layer of acousticallybenign material applied along the border of the first surface and eitherover or under the patch. Alternatively, the second acoustic element maycomprise acoustic material disposed on the patch over the cut-out. Insuch case, the second acoustic element may comprise acoustic materialthat has the same form as the cut-out and is disposed on the patch so asto be superimposed on the cut-out and the superimposed acoustic materialmay be aligned with the cut-out within 100 microns.

The reflective array may be disposed over the layer of acousticallybenign material along the border of the first surface; the cut-out andthe patch of the first acoustic element; and the second acousticelement, said propagating surface acoustic waves intercepted by thefirst acoustic element comprising a portion of the surface acousticwaves interacting with the reflective array, or the reflective array maybe disposed over the layer of acoustically benign material along theborder of the first surface; the first acoustic element; and the secondacoustic element, said propagating surface acoustic waves intercepted bythe first acoustic element comprising a portion of the surface acousticwaves interacting with the reflective array.

The cut-out may comprise a plurality of shapes and the second acousticelement is formed with a shape that is a composite of the plurality ofthe shapes of the cut-out, or the cut-out may comprise a plurality ofseparated shapes and the second acoustic element comprises a pluralityof separated segments that are interspersed among the shapes, eachsegment disposed adjacent a respective shape and at least partiallyintercepting the propagating surface acoustic waves intercepted by therespective shape.

Further, the second acoustic element may comprise an extension of thepatch disposed over the layer of acoustically benign material thatintercepts at least a portion of the propagating surface acoustic wavesthat are parallel to the propagating surface acoustic waves interceptedby the patch. The extension of the patch may comprise a first portionthat intercepts surface acoustic waves traveling in a first directionand a second portion that intercepts surface acoustic waves traveling ina second direction perpendicular to the first direction. Alternatively,the extension of the patch comprises either a layer of glass frit or alayer of glass frit disposed on a layer of acoustic material which isthe same as the patch acoustic material applied over the cut-out.

Further, the reflective array may be disposed over the layer ofacoustically benign material along the border of the first surface andat least a portion of the cut-out and the patch of the first acousticelement, said propagating surface acoustic waves intercepted by thefirst acoustic element comprising a portion of the surface acousticwaves interacting with the reflective array, and the second acousticelement may comprise the portion of the reflective array disposed overthe cut-out and the patch, said portion having a higher density ofreflector elements than the remainder of the reflective array. Thehigher density may maintain reflector element spacing equal to anintegral multiple of the surface acoustic wave wavelength transmitted bythe transducer. Alternatively, the higher density may obtain a desiredphase velocity of the surface acoustic waves transmitted by thetransducer.

The present invention also provides a method of compensating forattenuated signals received by an acoustic wave transducer in anacoustic touch apparatus having a substrate with at least two surfacescapable of propagating surface acoustic waves and acoustic materialdisposed on one of the propagating surfaces that forms an identificationmarking, comprising counteracting changes in the phase velocities of thepropagating surface acoustic waves passing over the disposed acousticmaterial. The counteracting step may comprise disposing a frit patternon the propagating surface adjacent the disposed acoustic material. Thecounteracting step may comprise equalizing the phase velocities of thebeams that comprise the propagating surface acoustic waves passing overthe disposed acoustic material.

The present invention also provides a method of providing an acoustictouch apparatus with a frit pattern that is associated with an iconlocated on a propagating surface of a substrate of the apparatus,comprising forming the frit pattern with an acoustic material thatprovides a gradated compensation of changes to the velocities of thesurface acoustic waves from the propagating surface through the icon.

The present invention also provides a method of providing an acoustictouch apparatus with a frit pattern to counteract changes in the phasevelocities of propagating surface acoustic waves passing over acousticmaterial that is disposed on a propagating surface of a substrate of theapparatus and that forms an identification marking, comprising formingthe frit pattern with a first segment that leads into one end of thelength of the identification marking and a second segment that leadsinto the opposite end of the length of the identification marking;forming the segments of the frit pattern with graded dimensions thatprovide a gradated change in the phase velocities of the surfaceacoustic waves from the surrounding propagating surface to theidentification marking; and adjusting the frit pattern, as needed, toaccommodate the layout and the particular features on the propagatingsurface. The method may further comprise forming the frit pattern withat least one third segment that fills in at least one area of thepropagating surface surrounding the identification marking. The methodmay further comprise juxtaposing the segments of the frit pattern andthe identification marking in a compact manner.

The present invention also provides an acoustic touch apparatus,comprising a first corrective structure for transmitted surface acousticwave (SAW) rays propagating parallel to the reflective array axisthrough an identification marking on the propagating surface, said firststructure providing correction for phase velocity shifts to onedirection of SAW propagation. The first structure may provide correctionfor refractive bending of transmitted SAW rays. The first structure maycomprise additional reflective array elements for obtaining a desiredphase velocity of transmitted SAW rays propagating through thereflective array. The first structure may comprise acoustic materialapplied over the identification marking to compensate for errantscattering of transmitted SAW rays by the identification marking.

The apparatus may further comprise a second corrective structure forscattered SAW rays propagating perpendicular to the reflective arrayaxis through the identification marking, said first and secondstructures providing correction for phase velocity shifts simultaneouslyto two different directions of SAW propagation. The first and secondcorrective structures may comprise acoustic material on the propagatingsurface that equalizes the phase velocities of the SAW rays propagatingthrough the identification marking. The first and second correctivestructures may comprise acoustic material on the propagating surfacethat equalizes the phase velocities of the SAW rays propagating throughthe identification marking with the SAW rays propagating apart from theidentification marking. The first structure may provide correction forrefractive bending of transmitted SAW rays and the second structure mayprovide correction for refractive bending of deflected SAW rays.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is madeto the following description of exemplary embodiments thereof, and tothe accompanying drawings, wherein:

FIG. 1 is a simplified cross-sectional view of an acoustic touch sensor;

FIGS. 2(A) and 2(B), respectively, are front and back plan views of thesubstrate of the acoustic touch sensor of FIG. 1;

FIG. 3 is a back plan view of the substrate of an acoustic touch sensorwith a logo/icon on the substrate;

FIG. 4A is a view of a portion of the back surface of the substrate ofan acoustic touch sensor prior to the application of a border layer;

FIG. 4B is a view of the back surface of FIG. 4A after the applicationof a border layer and a cut-out logo/icon;

FIG. 4C is a view of the back surface of FIG. 4B after the applicationof a color patch over the logo/icon;

FIG. 4D is a view of the back surface of FIG. 4C after the applicationof a reflective array over the border layer, the logo/icon, and thecolor patch;

FIG. 4E is a view of the back surface of FIG. 4D and directions ofsurface acoustic wave propagation;

FIG. 5 is a view of the back surface of the substrate of an acoustictouch sensor having a border layer, a cut-out logo/icon, and acompensating frit pattern constructed in accordance with a specificembodiment of the present invention;

FIG. 6 is a view of the back surface of the substrate of an acoustictouch sensor having a border layer, a cut-out logo/icon, a color patch,and a compensating frit pattern applied over the logo/icon constructedin accordance with a specific embodiment of the present invention;

FIG. 7A is a view of the back surface of the substrate of an acoustictouch sensor having a border layer, a cut-out logo/icon, and a colorpatch and surface acoustic waves transmitted partially through the colorpatch;

FIG. 7B is a view of the back surface of FIG. 7A with an enlarged colorpatch constructed in accordance with the present invention and surfaceacoustic waves transmitted through the enlarged color patch;

FIG. 7C is a view of the back surface of FIG. 7B and scattered surfaceacoustic waves transmitted partially through the enlarged color patch;

FIG. 7D is a view of the back surface of FIG. 7B with a reconfiguredcolor patch constructed in accordance with a specific embodiment of thepresent invention and scattered surface acoustic waves transmittedpartially through the reconfigured color patch;

FIG. 7E is a view of the back surface of FIG. 7B with a compensatingfrit layer constructed in accordance with the present invention andscattered surface acoustic waves transmitted partially through the fritlayer;

FIG. 8 is a view of the back surface of the substrate of an acoustictouch sensor having a reflective array design constructed in accordancewith a specific embodiment of the present invention;

FIG. 9 is a view of the back surface of the substrate of an acoustictouch sensor having a compensating frit pattern constructed inaccordance with a specific embodiment of the present invention;

FIG. 10A is a view of a portion of the back surface of the substrate ofan acoustic touch sensor;

FIG. 10B is a view of the back surface of FIG. 10A after the applicationof a logo/icon;

FIG. 10C is a view of the back surface of FIG. 10B after the applicationof a border layer over the logo/icon;

FIG. 10D is a view of the back surface of FIG. 10C after the applicationof a reflective array over the border layer and the logo/icon;

FIG. 10E is a view of the back surface of FIG. 10D and directions ofsurface acoustic wave propagation;

FIG. 11 is a view of the back surface of FIG. 10E having a compensatingpattern constructed in accordance with a specific embodiment of thepresent invention;

FIG. 12 is a view of the back surface of FIG. 11 having an additionalcompensating pattern constructed in accordance with a specificembodiment of the present invention; and

FIG. 13 is a view of a portion of the back surface of the substrate ofan acoustic touch sensor having a compensating pattern constructed inaccordance with a specific embodiment of the present invention.

FIG. 14A is a view of a portion of the back surface of the substrate ofan acoustic touch sensor having a compensating pattern constructed inaccordance with another specific embodiment of the present invention.

FIG. 14B is a view of a portion of the back surface of the substrate ofan acoustic touch sensor having a compensating pattern constructed inaccordance with yet another specific embodiment of the presentinvention.

FIG. 14C is a view of a portion of the back surface of the substrate ofan acoustic touch sensor having a split compensating pattern constructedin accordance with another specific embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

FIG. 1 shows a simplified cross-sectional view of an acoustic touchsensor 1. The touch sensor 1 comprises a substrate 5 with a frontsurface 10, a back surface 15, and connecting surfaces 20 joining theperipheral regions 14 of the front surface 10 and of the back surface15. A connecting surface 20 need not be curved as shown but generallycan have any shape that supports transfer of surface acoustic wavesbetween the front and back surfaces 10, 15. The substrate 5 is typicallymade of some form of glass which overlies a computer display orcomputing device display 25, like a liquid crystal display (LCD), acathode ray tube (CRT), plasma, etc. In a bezeled surface acoustic wavetouch sensor, the peripheral region 14 of the front surface 10 iscovered by a bezel provided by the housing of the touch sensor 1 or thedevice integrating the sensor 1, since the transducers and reflectivearrays are on the front surface 10 of the substrate 5. In a bezel-lesssurface acoustic wave touch sensor, which is shown in the figures, theperipheral region 14 of the front surface 10 is merely theouter/peripheral portion of the front surface 10 and no bezel isrequired of the associated housing as there are no exposed transducersand reflective arrays. Note that the terms “bezeled” and “bezel-less”are adjectives that do not describe the structure of the touch sensoritself, but rather describe how the touch sensor is integrated into alarger mechanical assembly. Bezel-less surface acoustic wave touchsensors are described in more detail in U.S. patent application Ser. No.13/012,513, entitled “BEZEL-LESS ACOUSTIC TOUCH APPARATUS” by Tanaka etal., filed on Jan. 24, 2011, which is herein incorporated by reference.Object 30 is seen in FIG. 1 as a finger, but it is recognized thattouches sensed by the surface acoustic waves may include a styluspressing against the front surface 10 directly or indirectly, through acover sheet or like element, depending upon the application of the touchsensor 1. Acoustic transducers 35 and reflective element arrays 40 areprovided on a border layer 27 of paint or ink (discussed further below)in the peripheral region 14 of the back surface 15. The transducers 35are operably coupled to a controller or control system 29 (which may bepart of a system processor in some embodiments) that is also operablycoupled to the display 25. The controller or control system 29 drivesthe operation of the transducers 35 and measures the signals from suchtransducers to determine the touch coordinates, which are then providedto an operating system and software applications to provide the requireduser interface with the display 25.

FIGS. 2(A) and 2(B), respectively, are front and back views of the touchsubstrate 5. In FIG. 2(A), which is a plan view of the front surface 10,the acoustic transducers 35 a, 35 b, 35 c, 35 d are shown in dotted lineto provide a frame of reference in relation to FIG. 2(B), which is aplan view of the back surface 15, where the transducers 35 a, 35 b, 35c, 35 d are situated and shown in solid line. Also, the peripheralregion 14 is shown in dotted line in FIGS. 2(A) and 2(B) and applies toboth surfaces 10, 15 of the touch substrate 5. To provide a furtherframe of reference, X-Y coordinate axes are shown in FIGS. 2(A) and2(B).

The front surface 10 has an inner portion 13 shown within dotted linesin FIG. 2(A), and optionally also an outer/peripheral portion 14, form anominal touch region on which the object 30 creates a contact to provideinput according to the graphical user interface shown on the display 25(shown in FIG. 1) disposed behind the back surface 15 and visiblethrough the transparent substrate 5. In some bezel-less acoustic touchsensors, the nominal touch region may also comprise the curvedconnecting surfaces 20 or portions thereof. For a bezeled surfaceacoustic wave touch sensor, the inner portion 13 not covered by a bezelforms the touch region.

The touch sensor 1 has two pairs of transducers 35 respectively for theX and Y axes that are located in the peripheral region 14 of the backsurface 15. The two pairs of transducers 35 are disposed at right anglesto define a two-dimensional coordinate system. In particular, a firsttransmitting transducer 35 a is placed in a Y-axis transmitting area anda second transmitting transducer 35 b is placed in an X-axistransmitting area. A first receiving transducer 35 c is placed in aY-axis receiving area opposite the Y-axis transmitting area. A secondreceiving transducer 35 d is placed in an X-axis receiving area oppositethe X-axis transmitting area. The first transmitting transducer 35 a andfirst receiving transducer 35 c are used to detect the touch positionsof the Y-coordinate on the front substrate 10, and the secondtransmitting transducer 35 b and second receiving transducer 35 d areused to detect touch positions of the X-coordinate on the frontsubstrate 10. Each transducer 35 may either transmit or receive asurface acoustic wave, symmetrically. The touch sensor 1 also includes apair of Y-axis reflective arrays 40 a, 40 b and a pair of X-axisreflective arrays 40 c, 40 d that are located in the peripheral region14 of the back surface 15 in the respective transmitting and receivingareas. The reflective arrays 40 reflect a surface acoustic wave in adesired direction, as described below.

As noted above, the touch sensor 1 is operatively connected with acontrol system 29 (shown in FIG. 1) for the associated computer orcomputing device that integrates the sensor 1. The control system 29generates an electronic signal that excites the transmitting transducers35 a, 35 b to generate respective surface acoustic waves (or wavepulses). The control system 29 also receives respective electricalsignals transduced by the receiving transducers 35 c, 35 d from thereceived surface acoustic waves. The control system 29, as used herein,means electronics typically including a microprocessor with firmware andanalog electronics to generate excitation signals and to receive backand analyze signals from the touch sensor 1.

In operation, the first transmitting transducer 35 a generates surfaceacoustic waves that travel along the negative (−) Y-axis direction ofthe peripheral region 14 of the back surface 15 on which the firstY-axis reflective array 40 a is situated. The elements of the firstY-axis reflective array 40 a each transmit part of the surface acousticwaves to an adjacent element of the array 40 a. Also, as seen by thesolid line arrows indicating the wave propagation path in FIGS. 2(A) and2(B), the elements of the first Y-axis reflective array 40 a each coupleor reflect part of the surface acoustic waves to travel a) from thefirst Y-axis reflective array 40 a outwardly along the negative (−)X-axis direction toward and around the proximate curved connectingsurface 20; b) along the positive (+) X-axis direction across the frontsurface 10 toward and around the opposing curved connecting surface 20;and then c) along the negative (−) X-axis direction to the second Y-axisreflective array 40 b on the back surface 15. The elements of the secondY-axis reflective array 40 b each transmit the received surface acousticwaves to an adjacent element of the array 40 b so that the wavescontinue traveling along the second Y-axis reflective array 40 b alongthe positive (+) Y-axis direction to the first receiving transducer 35c.

Similarly, the second transmitting transducer 35 b generates surfaceacoustic waves that travel along the negative (−) X-axis direction ofthe peripheral region 14 of the back surface 15 on which the firstX-axis reflective array 40 c is situated. The elements of the firstX-axis reflective array 40 c each transmit part of the surface acousticwaves to an adjacent element of the array 40 c. Also, as seen by thesolid line arrows indicating the wave propagation path in FIGS. 2(A) and2(B), the elements of the first X-axis reflective array 40 c each coupleor reflect part of the surface acoustic waves to travel a) from thefirst X-axis reflective array 40 c outwardly along the negative (−)Y-axis direction toward and around the proximate curved connectingsurface 20, b) along the positive (+) Y-axis direction across the frontsurface 10 toward and around the opposing curved connecting surface 20;and then c) along the negative (−) Y-axis direction to the second X-axisreflective array 40 d on the back surface 15. The elements of the secondX-axis reflective array 40 d each transmit the received surface acousticwaves to an adjacent element of the array 40 d so that the wavescontinue traveling along the second X-axis reflective array 40 d alongthe positive (+) X-axis direction to the second receiving transducer 35d.

A touch of the nominal touch region 13 (optionally including region 14)by an object 30, such as finger or stylus, absorbs a portion of theenergy of the surface acoustic waves propagating across the frontsurface 10 and causes an attenuation of the waves passing through thepoint of touch. The resulting attenuation is detected by the receivingtransducers 35 c, 35 d as a perturbation in the acoustic signal. Thecontrol system processes and analyzes the electrical signals transducedby the receiving transducers 35 c, 35 d, including those related towaveform perturbations, to detect the touch coordinates and positioninformation. Further, the control system maps the touch coordinates andposition information to the appropriate control actions of the userinterface shown in the display 25 that is generally placed behind theback surface 15. The acoustic touch sensor 1 thus provides an XYcoordinate input device system.

FIG. 3 is a plan view of a back surface 115 of a substrate 105 of anacoustic touch sensor 101 that has an exemplary logo/icon provided onthe substrate 105. As noted above, for a bezel-less acoustic touchsensor 101 that has certain aesthetic considerations, an acousticallybenign layer (“border layer”) 27 such as an opaque paint or ink (shownin FIG. 1) may be applied (e.g., screen printed, painted, sputtered orotherwise applied) on the peripheral region 114, or border, of the backsurface 115. The border layer 27 is acoustically benign, i.e., itpropagates surface acoustic waves without rapid attenuation, preferablyresulting in only small changes to the surface acoustic wave's velocityof propagation for easier manufacturing control of the wave's velocitydespite factional changes in material thickness. The border layer 27 maybe an inorganic black paint made of ceramic resin or porcelain enameltypes of material. Typically, the border layer 27 will be approximately10 microns thick, according to a specific embodiment. The peripheryfunctional elements, i.e., the transducers 135 and the reflective arrays140, are bonded on top of the border layer 27 so that the elements arehidden from view through the substrate 105 which is typicallytransparent. Other periphery elements are also laid on top of the borderlayer 27 to be hidden from view, e.g., mounting tape 152, sealing foam154. The border layer 27 is able to both bond with the substrate 105 andserve as an adequate processing surface for the transducers 135 and thereflective arrays 140 formed thereon. Note that the border layer 27 isnot shown in FIG. 3 so as not to obscure the structures but the borderlayer 27 covers the peripheral region 114, and may extend at least fromthe edges of the back surface 115 to just beyond the innermost edge ofthe mounting tape 152.

The exemplary logo/icon, and the layered material structures around thelogo/application icon, is described in more detail with respect to FIGS.4A through 4E. FIG. 4A shows a portion of the back surface 115 of thesubstrate 105 of the acoustic touch sensor 101 prior to the applicationof a border layer and a logo/icon. The dotted line indicates theboundary between the back surface 115 and the curved connecting surface20 of the substrate 105. FIG. 4B shows that the border layer 27 may beapplied on the peripheral region 114, or border, of the back surface115. However, the border layer 27 is not applied in regionscorresponding to the elements and shapes of the logo/icon 200. In thisway, the logo/icon 200 is formed by a “negative” process in which therespective elements and shapes are determined by the absence of the inkof the border layer 27. Note, although the present invention isdescribed herein with respect to logos or icons formed by a negativeprocess, the present invention may be applied with minor variations tothe case in which the logos and icons may be formed by a positiveprocess in which the respective elements and shapes are provided, suchas by printing, directly on the periphery back surface 115 of thesubstrate 105 underneath the border layer 27. This is described in moredetail in FIGS. 10-12.

FIG. 4C shows a color (e.g. silver) patch 210 that is applied (e.g.,glazing) over the elements and shapes of the logo/icon 200 and thenearby portion of the border layer 27. The patch 210 may be aninorganic, ceramic ink that provides a simple, cost-effective way tofill the empty elements and shapes of the logo/icon 200 and provides auniform color for the logo/icon 200. Alternatively, the empty elementsand shapes of the logo/icon 200 may be filled in directly with colorink. The patch 210 covers the entire logo/icon 200 but does not have tobe perfectly aligned. Typically, the patch 210 will be approximately 30microns thick.

As shown in FIG. 4D, the reflective arrays 140 are printed on top of theborder layer 27 so as to be hidden from view through the substrate 105which is typically transparent. The reflective arrays 140 may or may notbe printed on top of the patch 210. The figure shows the reflectivearray 140 partially printed on top of the patch 210. In this case, thelogo/icon 200 intercepts both the surface acoustic waves along the array140 axis from (or to) the transducer 135 as well as the scatteredsurface acoustic waves to (or from) the glass edge 20. FIG. 4E showssample SAW propagation directions 220 a, 220 b for the surface acousticwaves along the array 140 axis and for the scattered surface acousticwaves.

As indicated above, the presence of a logo/icon 200 may cause reducedreceived signals in the acoustic touch sensor 101 due to 1) lens orrefraction effects; 2) scattering effects; and 3) phase velocity shifteffects on array reflector spacing. The first problem of lens orrefraction, for example, due to regions of missing border layer 27corresponding to logo lettering, may be addressed by considering onlythe transducer beam energy through the logo/icon 200. This is shown inFIG. 5, where the color patch 210 and the reflector array 140 arepresent but are not shown for clarity. As noted above, during operationof the touch sensor 101, a depression in the signal past (or downstream)the logo/icon 200 may result due to undesired lensing or refraction ofSAW beams passing through the logo/icon 200. This results in changes inthe received signal. To compensate for the logo/icon 200 in accordancewith the present invention, a pattern of acoustic material (e.g., glassfrit) 225 is printed in the neighborhood of the logo/icon 200, eitherbefore (as shown), after, or between the elements and shapes of thelogo/icon 200. In particular, the phase delays in the added glass fritcorrection “lens” 225 cancels the phase advance where ink of the borderlayer 27 is missing in the elements and shapes of the logo/icon 200. Incertain circumstances, the frit pattern 225 may appear to largely orentirely eliminate any depression of the signal after the logo/icon 200.

The frit pattern 225 and the reflective array 140 are applied on theback surface 115 after the application of the border layer 27. It may beapplied before, after, or at the same time as the application of thecolor patch 210. The frit pattern 225 may be applied on the back surface115 by various methods (e.g., screen printed, painted, sputtered, orotherwise applied). The frit pattern 225 may take on any shape, may beplaced upstream or downstream of the wave propagation, and may beinterspersed with the elements and shapes of the logo/icon 200. Thecritical characteristic of the frit pattern 225 is the ability to enablethe total phase velocity of the surface acoustic waves travellingthrough the logo/icon 200 to be effectively the same for the differentbeams of the surface acoustic waves. FIG. 5 shows the frit pattern 225taking on a shape that is a composite of the elements and shapes of thelogo/icon 200 that are downstream. This equalizes the variations in thephase delay of the horizontally-shown propagating SAW paths through thefrit pattern 225 and the logo/icon 200.

Alternatively, in the case that the SAW velocity loading effect is thesame for the border layer 27 and the frit pattern 225, the frit pattern230 may be applied on the color patch 210 over the elements or shapes ofthe logo/icon 200 like a second patch. This is shown in FIG. 6. Notethat it is also applied before the application of the reflective array.If the frit pattern 230 has a weaker SAW velocity loading effect, thecompensation is partial but still beneficial. If the frit pattern 230has a stronger SAW velocity loading effect, the effective area averageprint thickness may be reduced, for example, with a fine mesh patternfor the frit pattern 230. This approach is possible because there are nodemanding optical requirements for the logo/icon 200 that would beadversely affected by printed material “within” the logo/icon 200.

The first problem of lens or refraction effects also arises in the casewhere the surface acoustic waves from the transducer 135 are transmittedthrough the color patch 210. As illustrated in FIG. 7A, a SAW ray 235just above the color patch 210 will advance in phase relative to a SAWray 240 through the color patch 210 due to the phase velocity slowingeffects of the color patch 210. This rotation of the equal phase wavefront leads to refractive bending 245 of the transmitted SAW beam. Asillustrated in FIG. 7B, the simplest approach to address this problem isto increase the width of the color patch 210 to intercept the entireuseful width of the transducer SAW beam. In such case, the SAW ray 235just above the color patch 210 will have the same phase velocityrelative to the SAW ray 240 through the color patch 210 and norefractive bending of the transmitted SAW beam occurs. The figure doesnot show the reflective array (for ease of visualization) but the entireuseful width may be at least the width of the reflective array plus someadditional space, e.g., two to three mm, on each side. Note that,typically, the edge of the substrate 105 is relatively distant from thereflective array, the logo/icon 200, and the color patch 210 (a fewmillimeters) so that an enlarged color patch 210 may be accommodated.

FIG. 7C is a view of the back surface of FIG. 7B and scattered surfaceacoustic waves transmitted partially through the enlarged color patch210. More particularly, the SAW rays 235, 240 transmitted from thetransducer (not shown) propagate horizontally through the enlarged colorpatch 210 with the same phase velocity. However, the SAW rays 235, 240are partially reflected or scattered by the reflective array 140 topropagate vertically. In the figure, the phase of the scattered SAW ray235 in the color patch 210 is slowed relative to the scattered SAW ray240 outside of the color patch 210, leading to refractive SAW deflection250. If there is sufficient space between the edge of the substrate 105and the SAW beam transmitted parallel to the array axis (i.e.,transmitted from the transducer), the refractive SAW deflection 250 maybe partially compensated by a reconfigured color patch 210 that providesextra printed material 255 a, 255 b parallel to the substrate 105 edgeto partially intercept the scattered SAW ray 240. This is shown in FIG.7D. This will have the effect of slowing down the scattered SAW ray 240relative to the phase velocity of the scattered SAW ray 235 in the colorpatch 210 and partially correcting the refractive SAW deflection 250.The extensions 255 a, 255 b of the reconfigured color patch 210 parallelto the substrate 105 edge may be gradually tapered (e.g., formedV-shaped) so that they do not need to extend the entire length of theedge.

Stronger phase compensation for the scattered SAW ray 235 is possiblewith the addition of a frit layer 260 printed on top of or underneaththe reconfigured color patch 210 extensions 255 a, 255 b. This is shownin FIG. 7E. Alternatively, the frit layer may be used in lieu of thereconfigured color patch 210 extensions 255 a, 255 b. The frit layer 260also may be gradually tapered (e.g., formed V-shaped) so it does notneed to extend the entire length of the substrate 105 edge. Regardlessof the configuration, the frit layer may be formed to equalize the phasevelocities of the SAW rays 235, 240 to eliminate the refractive SAWdeflection 250.

The present invention also addresses the problem of the undesiredeffects of phase velocity shifts, caused by the presence of thelogo/icon 200, on reflective array spacing. Ideally, reflective arraysare spaced at integral multiples of the SAW wavelength. For a givenoperating frequency of the acoustic touch sensor 101, the SAW wavelengthis equal to the SAW phase velocity divided by the operating frequency.So when the phase velocity of a SAW beam changes, the SAW wavelengthalso changes. As described above, the color patch 210 for the logo/icon200 decreases the phase velocity of SAW beams propagating through thecolor patch 210 and, consequently, locally reduces the SAW wavelength.If the reflector array spacing is not modified to compensate for thereduced SAW phase velocity, and hence reduced SAW wavelength, arrayreflection will become less coherent resulting in a dip in the receivedsignal corresponding to the width of the color patch 210. As shown inFIG. 8, the present invention provides a reflective array 140 designthat may compensate for this adverse effect with a decrease in array 140spacing within the color patch 210 (e.g., by the addition of reflectivearray elements 265) to maintain a spacing equal to an integral number ofSAW wavelengths. It is noted, for visual clarity, FIG. 8 greatlyexaggerates the change in reflective array 140 spacing; in actualacoustic touch sensor 101 designs, the change in reflective array 140spacing will be on the order of 1% or less.

The present invention also addresses the undesired effect that thelogo/icon 200 itself or the color patch 210 may be a source of undesiredSAW reflections and subsequent parasitic received signals. Asillustrated in FIG. 9, a horizontal arrow 270 represents a reflection ofa transmitting transducer's SAW beam 275 off the leading vertical edgeof the color patch 210. This reflection is not of serious concern as thesmall amount of reflected SAW energy in this case is unlikely to make itto the receiving transducer (not shown) and create a parasitic signal. Avertical arrow 277 represents a 90° SAW beam scattering off the portionof the outline of the logo/icon 200 letter “o” that is at 45° (insteadof scattering off one of the reflective array 140 elements). This is ofmore serious concern as the scattered beam may follow an acoustic pathto the receiving transducer. The present invention provides an oppositephase (180°) reflection in the same direction to counteract the errantscattering via destructive interference. Specifically, a frit pattern280 may be applied on the color patch 210 over the elements or shapes ofthe logo/icon 200, like a second patch, but before the application ofthe reflective array 140. The frit pattern 280 must be aligned with theelements or shapes of the logo/icon 200 (e.g., within 100 microns, orother small fraction of a wavelength) to maximize its compensatingeffect. In such case, the frit pattern 280 significantly reduces oreliminates the undesired reflection. Note that, in many cases, suchlogo/icon 200 reflections may be present but at too low of a level tocause significant degradation in acoustic touch sensor performance.Also, modifications to the location or form of the elements or shapes ofthe logo/icon 200 may assist in minimizing undesired signal effects incombination with the present invention, or alone.

As noted above, the present invention may be applied with minorvariations to the case in which the logos and icons may be formed by a“positive” process in which the respective elements and shapes areprovided, such as by printing, directly on the periphery of the backsurface 115 of the substrate 105 underneath the border layer 27. Theacoustic touch sensor 101 with an exemplary positive logo/icon 300fabricated on the back surface 115 of the substrate 105 is described inmore detail in FIGS. 10-12. FIG. 10A is a view of a portion of the backsurface 115 of the substrate 105 of the acoustic touch sensor 101. Thedotted line indicates the boundary between the back surface 115 and thecurved connecting surface 20 of the substrate 105. FIG. 10B is a view ofthe back surface 115 after the application of an exemplary logo/icon 300on the substrate 105. FIG. 10C is a view of the back surface 115 afterthe application of a border layer 27 over the peripheral region 114 ofthe back surface 115, including the logo/icon 300. This permits thelogo/icon 300 (also referred to as printed material 300) to be seenthrough the substrate 105 which is typically transparent. The printedmaterial 300 is acoustically benign like the border layer 27 and may bemade of similar materials (although of different pigmentations so as tobe distinguished). The printed material 300 may be applied on the backsurface 115 by various methods (e.g., screen printed, painted,sputtered, or otherwise applied). Typically, the printed material 300has more layers of ink than the border layer 27.

As shown in FIG. 10D, the reflective arrays 140 are printed on top ofthe border layer 27 so as to be hidden from view through the substrate105. The reflective arrays 140 may or may not be printed above thelogo/icon 300. The figure shows the reflective array 140 partiallyprinted above the logo/icon 300. In this case, the logo/icon 300intercepts both the surface acoustic waves along the array 140 axis from(or to) the transducer 135 (not shown) as well as the scattered surfaceacoustic waves to (or from) the glass edge 20. FIG. 10E shows sample SAWpropagation directions 220 a, 220 b for the surface acoustic waves alongthe array 140 axis and for the scattered surface acoustic waves.

Like a logo/icon fabricated with a negative process, the presence of alogo/icon 300 fabricated with a positive process may cause reducedreceived signals in the acoustic touch sensor 101 due to 1) lens orrefraction effects; 2) scattering effects; and 3) phase velocity shifteffects on array reflector spacing. The present invention providessimilar solutions to those applied above to correct for a logo/iconformed with a negative process. FIG. 11 is a view of the back surface115 of the substrate 105 having a compensating pattern 305, constructedin accordance with the present invention, to compensate for thelogo/icon 300. The compensating pattern 305 comprises a pattern ofacoustic material (e.g., glass frit or material similar to the materialof the logo/icon 300) that is printed next to the logo/icon 300 toenable phase velocity changes of the transmitted SAW 220 a through thelogo/icon 300. In particular, the phase delays in the added compensatingpattern 305 cancel the phase advance where ink of the border layer 27doesn't overlie the elements and shapes of the logo/icon 200. In certaincircumstances, the compensating pattern 305 may appear to entirelyeliminate any phase shifting (and signal dipping) of the receivedsignal.

The compensating pattern 305 is shown comprising multiple segments 305a, 305 b, 305 c, 305 d, each of which are positioned adjacently above arespective element or shape of the logo/icon 300. Each segment also hasa width that roughly corresponds to the width of the respective elementor shape of the logo/icon 300. The compensating pattern 305 may beapplied before or after the application of the border layer 27 and,alternatively, may be applied at the same time as the reflective array140. The compensating pattern 305 may be applied by various methods(e.g., screen printed, painted, sputtered, or otherwise applied). Thecompensating pattern 305 may take on any shape (although shown asrectangular as well as segmented), may be placed upstream or downstreamof the wave propagation, and may be interspersed with the elements andshapes of the logo/icon 300 (as shown). The critical characteristic ofthe compensating pattern 305 is the ability to enable the total phaseadvance of the surface acoustic waves travelling through the logo/icon300 to be effectively the same for the different beams of the surfaceacoustic waves. FIG. 11 shows the compensating pattern 305 taking on aninterspersed, segmented form that approximates the forms of the elementsand shapes of the logo/icon 300. This equalizes the variations in thephase delay of the horizontally-shown propagating SAW paths 220 athrough the compensating pattern 305 and the logo/icon 300.

While FIG. 11 shows a compensating pattern 305 that equalizes phaseshifts of horizontal (i.e., transmitted) SAW beams as a function ofheight (or the vertical coordinate), FIG. 12 shows an additionalcompensating pattern 310 that equalizes phase shifts of vertical (i.e.,scattered) SAW beams through the logo/icon 300 as a function of thehorizontal coordinate. The compensating pattern 310 comprises a patternof acoustic material (e.g., glass frit or material similar to thematerial of the logo/icon 300) that is printed next to the logo/icon 300to enable phase velocity changes of the scattered SAW 220 b through thelogo/icon 300. In particular, the phase delays in the added compensatingpattern 310 cancel the phase advance where ink of the border layer 27doesn't overlie the elements and shapes of the logo/icon 200. Like thefirst compensating pattern 305, in certain circumstances, thecompensating pattern 310 may appear to entirely eliminate any phaseshifting (and signal dipping) of the received signal.

The compensating pattern 310 is shown comprising two segments 310 a, 310b, each of which is positioned adjacently below certain of the elementsor shapes of the logo/icon 300. Each segment also has a vertical profilethat roughly equalizes the vertical profiles of the respective elementor shape of the logo/icon 300. The compensating pattern 310 may beapplied before or after the application of the border layer 27 and,alternatively, may be applied at the same time as the reflective array140. The compensating pattern 310 may be applied by various methods(e.g., screen printed, painted, sputtered, or otherwise applied). Thecompensating pattern 310 may take on any shape, may be placed upstreamor downstream of the wave propagation, and may be interspersed with theelements and shapes of the logo/icon 300. The critical characteristic ofthe compensating pattern 310, like the first compensating pattern 305,is the ability to enable the total phase advance of the surface acousticwaves travelling through the logo/icon 300 to be effectively the samefor the different beams of the surface acoustic waves. As noted above,FIG. 12 shows the compensating pattern 310 taking on a segmented formthat roughly equalizes the vertical profiles of the respective elementor shape of the logo/icon 300. This equalizes the variations in thephase delay of the vertically-shown propagating SAW paths 220 b throughthe compensating pattern 310 and the logo/icon 300. Note that a segment310 a, 310 b of the compensating pattern 310 may extend, and be tapered(e.g., formed V-shaped), beyond the horizontal position of the logo/icon300. This provides a gradual change in phase shifting of the vertical(i.e., scattered) SAW beams 220 b through the logo/icon 300 relative tothe surrounding border layer 27.

Although the placement and form of either compensating pattern 305, 310are not critical factors to enable a gradual phase change of thereceived signal as desired, each may be adjusted to optimizecompensation. Since each logo or application icon is different than thenext, the placement and form of the compensating pattern 305, 310 may beadapted to meet the form of the logo or application icon. There are,however, general optimization techniques, that are generally shown inFIG. 13. For example, the compensating pattern 325, and each of itssegments 325 a, 325 b, 325 c, generally should be minimally displacedfrom the elements and shapes of the logo/icon 300. Also, leading andtrailing segments 325 a, 325 b may have graded dimensions (in threedirections) that are directed to a gradual phase change of the receivedsignal. Also, the compensating pattern 325 may be segmented to permit acloser matching with the respective elements and shapes of the logo/icon300 (for example, by using interspersed segments 325 c). However, forvarious reasons, it may not be possible to precisely follow any of thetechniques. In such case, the techniques may be adjusted to suit theparticular circumstance.

As illustrated in FIGS. 14A, 14B and 14C, when a logo/icon is placedentirely outside a reflective array, and furthermore there is additionalroom for compensating patterns outside of the arrays, an alternatemethod may be used to design the compensating pattern. Referring to FIG.14A, border layer 1027 on substrate 1005 with rounded connecting surface1020 includes a logo/icon 1200 in which border layer 1027 is absent.Reflective array 1040, and associated SAW rays such as SAW ray 1235 andSAW ray 1240, do not overlap logo/icon 1200 and furthermore there isspace available between reflective array 1040 and rounded connectingsurface 1020 in which to add a compensating frit pattern 1225.Compensating frit pattern 1225 prevents undesired deflections of SAWrays scattered by reflective array 1040 by the logo/icon 1200 viaassuring no net phase perturbation of SAW rays such as SAW ray 1250passing through the logo/icon 1200. For this purpose, the geometry ofthe frit compensation pattern 1225 may be a copy of the geometry of thelogo/icon 1200 with a compression (as shown) or dilation to account forthe difference in phase velocity shifts due to the material coating ofthe border layer 1027 and the material coating of the frit compensationpattern 1225. In particular, if V₀ is the SAW phase velocity of a baresurface of substrate 1005, V₁ is the SAW phase velocity where substrate1005 is coated with border layer 1027, and V₂ is the SAW phase velocitywhere substrate 1005 is coated with border layer 1027 and also frit ofthe compensating pattern 1225, then the compensation pattern 1225 ismagnified in the direction of SAW wave propagation through the logo/icon1200 by a factor given by the following formula.

Magnification factor=(V ₂ /V ₀)·(V ₀ −V ₁)/(V ₁ −V ₂)

If the magnification factor is one, the geometry of the fritcompensation pattern 1225 is identical to the geometry of the logo/icon1200. If the magnification factor is greater than one, the fritcompensation pattern 1225 is expanded (not shown) and if themagnification factor is less than one, the frit compensation pattern1225 is compressed as shown in FIG. 14A. Advantageously, the detailedgeometry of frit compensation pattern 1225 may be determined from thegeometry of icon/logo 1200 and SAW velocity data.

FIG. 14B illustrates a generalization of the principles of FIG. 14A tothe case where the substrate edge is not parallel to reflective arrayand furthermore may be gently curved. Border layer 2027 on substrate2005 with rounded connecting surface 2020 includes a logo/icon 2200 inwhich border layer 2027 is absent. Reflective array 2040, and associatedSAW rays such as SAW ray 2235 and SAW ray 2240, do not overlap logo/icon2200 and furthermore there is space available between reflective array2040 and rounded connecting surface 2020 in which to add a compensatingfrit pattern 2225. Compensating frit pattern 2225 prevents undesireddeflections of SAW rays scattered by reflective array 2040 by thelogo/icon 2200 via assuring no net phase perturbation of SAW rays suchas SAW ray 2250 passing through the logo/icon 2200. The geometry of thefrit compensation pattern 1225 may be a copy of the geometry of thelogo/icon 1200 with a compression (as shown) or dilation to account forthe difference in phase velocity shifts due to the material coating ofthe border layer 2027 and the material coating of the frit compensationpattern 2225. The compression or dilation of the frit compensationpattern is in the propagation direction of SAW passing through thelogo/icon, for example SAW ray 2250, but unlike the embodiment of FIG.14A, and as indicated by dashed lines 2260, the SAW propagationdirection is no longer in a vertical direction. Non-vertical SAW rayssuch as SAW ray 2250 may be desirable on the back surface of substrate2005 when the rounded connecting surface 2020 is curved and not parallelto reflective array 2040 so that on the front touch surface of substrate2005 the SAW rays, such as SAW ray 2251 (indicated with dashed lines)are vertical.

FIG. 14C illustrates the use of a split compensation pattern for caseswhere there is insufficient room for the complete compensation patternabove the icon or below the icon (unlike the embodiment of FIG. 14A). Inthe embodiment of FIG. 14C, there is insufficient room for a completefrit compensation pattern within border layer 3027 on substrate 3005between logo/icon 3200 and rounded connecting surface 3020. There isalso insufficient room for a complete frit compensation pattern betweenreflective array 3040 and logo/icon 3200. In such a case, thecompensation pattern may be split into a lower compensation patternportion 3225 a and an upper compensation pattern portion 3225 b as shownin FIG. 14C. Lower compensation pattern portion 3225 a and an uppercompensation pattern portion 3225 b together prevent undesireddeflections of SAW rays scattered by reflective array 3040 by thelogo/icon 3200 via assuring no net phase perturbation of SAW rays suchas SAW ray 3250 passing through the logo/icon 3200. Where possible, suchsplit compensation patterns may be desirable to minimize the distancebetween corresponding points in the logo/icon pattern and thecompensation pattern.

Advantageously, as described with the above embodiments, the presentinvention provides acoustic touch sensors that have correctivestructures for transmitted SAW rays propagating parallel to the arrayaxis through a logo/icon as well as for scattered SAW rays propagatingperpendicular to the array axis through the logo/icon, i.e., acoustictouch sensors that provide correction for logo/icon phase shiftssimultaneously to two different directions of SAW propagation.

Other modifications are possible within the scope of the invention. Forexample, in each embodiment described, the acoustic touch sensor 101 mayhave the reflective arrays 140 and the logo/icon 200, 300 (and the colorpatch 210) well separated. In this case, the logo/icon 200, 300 (and thecolor patch 210) intercepts only the scattered surface acoustic waves to(or from) the glass edge 20. Then, the acoustic touch sensor 101 onlyequalizes or avoids rapid variations in phase delay of verticallypropagating SAW paths as a function of the horizontal coordinate (orposition of the SAW path). This may be accomplished using any of theappropriate correction elements described above, for example, the fritpatterns 225, 230; the extensions 255 a, 255 b of the reconfigured colorpatch 210; the frit pattern 280; or the compensating pattern 310.

1. An acoustic touch apparatus, comprising: a substrate having surfacesconfigured to propagate surface acoustic waves; at least one acousticwave transducer on a first surface; and at least one reflective array onthe first surface, said transducer configured to at least transmit orreceive surface acoustic waves to or from the reflective array and saidreflective array configured to acoustically couple surface acousticwaves to propagate between surfaces of the substrate, and said substratehaving a first acoustic element disposed on the first surface that isconfigured to intercept propagating surface acoustic waves on the firstsurface and is configured to cause variations in the phase velocity ofthe propagating surface acoustic waves and a second acoustic elementdisposed on the first surface to equalize the variations, wherein thesecond acoustic element is formed with a shape that is a compensatingpattern of the first acoustic element.
 2. The apparatus of claim 1,wherein the second acoustic element is configured to cancel out thephase advance or delay of any portion of the propagating surfaceacoustic waves intercepted by the first acoustic element.
 3. Theapparatus of claim 1, wherein the second acoustic element is disposed onthe first surface in proximity to the first acoustic element.
 4. Theapparatus of claim 1, wherein the second acoustic element is disposed onthe first surface as physically close as possible to the first acousticelement.
 5. The apparatus of claim 1, wherein the second acousticelement is configured to intercept propagating surface acoustic wavesintercepted by the first acoustic element.
 6. The apparatus of claim 5,wherein the second acoustic element is configured to interceptpropagating surface acoustic waves parallel to the propagating surfaceacoustic waves intercepted by the first acoustic element.
 7. Theapparatus of claim 1, wherein the first acoustic element comprises apatch of acoustic material applied over a cut-out of a layer ofacoustically benign material applied along a border of the firstsurface.
 8. The apparatus of claim 7, wherein the layer of acousticallybenign material comprises a first opaque ink and the patch of acousticmaterial comprises a second opaque ink having different visualproperties than the first opaque ink.
 9. The apparatus of claim 1,wherein the first acoustic element comprises a cut-out of a layer ofacoustically benign material applied along a border of the first surfaceand an acoustic material filling in the cut-out, said first and secondmaterials being visually distinguished from one another.
 10. Theapparatus of claim 1, wherein the first acoustic element comprisesacoustic material applied on the first surface and disposed under alayer of acoustically benign material applied along a border of thefirst surface.
 11. The apparatus of claim 10, wherein the layer ofacoustically benign material comprises a first opaque ink and theacoustic material of the first acoustic element comprises a secondopaque ink having different visual properties than the first opaque ink.12. The apparatus of claim 7, wherein the second acoustic elementcomprises acoustic material disposed adjacent the cut-out over the layerof acoustically benign material applied along the border of the firstsurface and either over or under the patch.
 13. The apparatus of claim7, wherein the second acoustic element comprises acoustic materialdisposed on the patch over the cut-out.
 14. The apparatus of claim 10,wherein the second acoustic element comprises acoustic material disposedadjacent the first acoustic element and either over or under the layerof acoustically benign material applied along the border of the firstsurface. 15-25. (canceled)
 26. The apparatus of claim 7, wherein thereflective array is disposed over the layer of acoustically benignmaterial along the border of the first surface and at least a portion ofthe cut-out and the patch of the first acoustic element, saidpropagating surface acoustic waves intercepted by the first acousticelement comprising a portion of the surface acoustic waves that interactwith the reflective array.
 27. (canceled)
 28. (canceled)
 29. Theapparatus of claim 5, wherein the second acoustic element counteractsthe phase advance of any portion of the propagating surface acousticwaves intercepted by the first acoustic element.
 30. The apparatus ofclaim 6, wherein the second acoustic element counteracts the phaseadvance of a portion of the propagating surface acoustic waves parallelto the propagating surface acoustic waves intercepted by the firstacoustic element. 31-46. (canceled)
 47. The apparatus of claim 1,wherein the second acoustic element is formed with a composite of two ormore separated shapes that combine to form a split compensating patternof the first acoustic element.
 48. An acoustic touch apparatus,comprising: a substrate having surfaces configured to propagate surfaceacoustic waves; at least one acoustic wave transducer on a firstsurface; and at least one reflective array on the first surface, saidtransducer configured to at least transmit or receive surface acousticwaves to or from the reflective array and said reflective arrayconfigured to acoustically couple surface acoustic waves to propagatebetween surfaces of the substrate, and said substrate having a firstacoustic element disposed on the first surface that is configured tointercept propagating surface acoustic waves on the first surface and isconfigured to cause variations in the phase velocity of the propagatingsurface acoustic waves and a second acoustic element disposed on thefirst surface to equalize the variations, wherein the second acousticelement is formed with a composite of two or more separated shapes thatcombine to form a split compensating pattern of the first acousticelement.
 49. The apparatus of claim 48, wherein the second acousticelement is configured to cancel out the phase advance or delay of anyportion of the propagating surface acoustic waves intercepted by thefirst acoustic element.
 50. The apparatus of claim 48, wherein thesecond acoustic element is disposed on the first surface in proximity tothe first acoustic element.
 51. The apparatus of claim 48, wherein thesecond acoustic element is disposed on the first surface as physicallyclose as possible to the first acoustic element.
 52. The apparatus ofclaim 48, wherein the second acoustic element is configured to interceptpropagating surface acoustic waves intercepted by the first acousticelement.
 53. The apparatus of claim 52, wherein the second acousticelement is configured to intercept propagating surface acoustic wavesparallel to the propagating surface acoustic waves intercepted by thefirst acoustic element.
 54. The apparatus of claim 48, wherein the firstacoustic element comprises a patch of acoustic material applied over acut-out of a layer of acoustically benign material applied along aborder of the first surface.
 55. The apparatus of claim 54, wherein thelayer of acoustically benign material comprises a first opaque ink andthe patch of acoustic material comprises a second opaque ink havingdifferent visual properties than the first opaque ink.
 56. The apparatusof claim 48, wherein the first acoustic element comprises a cut-out of alayer of acoustically benign material applied along a border of thefirst surface and an acoustic material filling in the cut-out, saidfirst and second materials being visually distinguished from oneanother.
 57. The apparatus of claim 48, wherein the first acousticelement comprises acoustic material applied on the first surface anddisposed under a layer of acoustically benign material applied along aborder of the first surface.
 58. The apparatus of claim 57, wherein thelayer of acoustically benign material comprises a first opaque ink andthe acoustic material of the first acoustic element comprises a secondopaque ink having different visual properties than the first opaque ink.59. The apparatus of claim 54, wherein the second acoustic elementcomprises acoustic material disposed adjacent the cut-out over the layerof acoustically benign material applied along the border of the firstsurface and either over or under the patch.
 60. The apparatus of claim54, wherein the second acoustic element comprises acoustic materialdisposed on the patch over the cut-out.
 61. The apparatus of claim 57,wherein the second acoustic element comprises acoustic material disposedadjacent the first acoustic element and either over or under the layerof acoustically benign material applied along the border of the firstsurface.
 62. The apparatus of claim 52, wherein the second acousticelement counteracts the phase advance of any portion of the propagatingsurface acoustic waves intercepted by the first acoustic element. 63.The apparatus of claim 53, wherein the second acoustic elementcounteracts the phase advance of a portion of the propagating surfaceacoustic waves parallel to the propagating surface acoustic wavesintercepted by the first acoustic element.
 64. The apparatus of claim54, wherein the reflective array is disposed over the layer ofacoustically benign material along the border of the first surface andat least a portion of the cut-out and the patch of the first acousticelement, said propagating surface acoustic waves intercepted by thefirst acoustic element comprising a portion of the surface acousticwaves that interact with the reflective array.